Recently house gardening, such as in a vinyl house, is now at the zenith of its popularity and various farm products are shipped to market regardless of the season. Alternately, a greening plan of a space of a dwelling or building or structure, especially a roof space, is on its way to practicality and various devices and methods, which use a fibrous foamed mat or a light artificial soil or stone, have been proposed for the greening. Further, greening concrete, which is porous and can retain moisture therein, has also been proposed to cultivate the plants on a wall surface or an inclined surface or a structure, by seeding or transplantation of the plants on these surfaces.
However, the artificial soil or the fibrous foamed mat for the greening of the structure seems to be easily blown away or carried away by a storm or a strong rain, and may contaminate a dwelling's environment. The greening concrete also seems to be higher in price than the original one, and has fault in its strength due to its porous character.